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<body>
  <p>
     Commons-Collections contains implementations, enhancements and utilities
     that complement the Java Collections Framework.
  </p>
  <p>
     The Apache Commons Collections Framework component adds a significant
     amount of enhancements to the standard JDK collections. These enhancements
     come in the form of new interfaces, new implementations and utility classes.
  </p>
  <p>
     See also the {@code java.util} package for the standard Java collections.
  </p>
     
  <h1>Main features</h1>
  <p>
     Commons-Collections defines a number of key interfaces:
  </p>
  <table border="1">
  <caption>Interfaces</caption> 
  <tr class="TableHeadingColor">
    <th>Interface</th><th>Description</th>
  </tr>
  <tr>
    <td>
      {@link org.apache.commons.collections4.Bag}
    </td>
    <td>
      A new {@code Collection} subinterface that stores each object together
      with the number of occurrences. Methods are provided to get the number of
      occurrences, and to add and remove a certain number of that object.
    </td>
  </tr>
  <tr>
    <td>
      {@link org.apache.commons.collections4.BidiMap}
    </td>
    <td>
      A new {@code Map} subinterface that allows lookup from key to value and
      from value to key with equal ease.
    </td>
  </tr>
  <tr>
    <td>
      {@link org.apache.commons.collections4.OrderedMap}
    </td>
    <td>
      A new {@code Map} subinterface that is used when a map has an order, but is
      not sorted. Methods enable bidirectional iteration through the map.
    </td>
  </tr>
  <tr>
    <td>
      {@link org.apache.commons.collections4.MapIterator}
    </td>
    <td>
      A new {@code Iterator} subinterface specially designed for maps. This iterator
      avoids the need for entrySet iteration of a map, and is simpler to use.
    </td>
  </tr>
  <tr>
    <td>
      {@link org.apache.commons.collections4.ResettableIterator}
    </td>
    <td>
      A new {@code Iterator} subinterface that allows the iteration to be reset back
      to the start. Many iterators in this library have this functionality.
    </td>
  </tr>
  <tr>
    <td>
      <ul>
        <li>{@link org.apache.commons.collections4.Closure}</li>
        <li>{@link org.apache.commons.collections4.Predicate}</li>
        <li>{@link org.apache.commons.collections4.Transformer}</li>
        <li>{@link org.apache.commons.collections4.Factory}</li>
      </ul>
    </td>
    <td>
      A group of <i>functor</i> interfaces that provide plugin behavior to various
      collections and utilities.
    </td>
  </tr>
  </table>
  <p>
     In addition to the interfaces, there are many implementations.
     Consult each subpackage for full details of these.
  </p>
     
</body>
